Mercruiser Alpha I Zinc Anode Kit | Martyr CMALPHAGEN1KITZ Martyr anode kit includes all replacement anodes needed to protect Mercruiser Alpha 1 stern drives from corrosion in salt water. Mercruiser Alpha one stern drive anode kit For Mercruiser Alpha I drives from 1983 to 1990 Kit includes CM31640Z trim tab anode, (2) CM55989Z bolt nut anodes and CM821631Z gimbal block anode Zinc anodes for salt water applications Martyr anodes are made of a high purity specialized alloy based on the US Mil Spec Supplied with mounting hardware for anodes